A large number of proposals has been made for the formulation of fabric softening compositions, most of these involving the use of an aqueous dispersion of a cationic surfactant, for instance a quaternary ammonium salt or an imidazolinium salt, as the active component or as part of it. It is known from U.S. Pat. No. 4,308,024 corresponding to GB-A-2039556 that fabric softening compositions can be formulated to comprise a dispersion of cationic surfactant together with free fatty acid which functions as a nonionic surfactant.
The above compositions based on dispersions of cationic surfactants are non-Newtonian in character. In compositions intended for use by consumers in the home the viscosity (or strictly the apparent viscosity) of the composition is an important factor in its acceptability to the consumer, the more viscous compositions being perceived as being of higher quality than the more mobile ones. Manufacturers therefore attempt to produce a product which is as viscous as possible without being so viscous that problems are created elsewhere, such as in pouring or dispensing characteristics. In compositions intended for automated dispensing in washing machines, a low but tightly controlled viscosity is desirable, which again is difficult to achieve if the composition behaves unpredictably during manufacture and subsequent ageing.
U.S. Pat. No. 4,379,059 corresponding to EP-51983 discloses a process for the manufacture of a shear-thinning fabric softening composition, with good control of final viscosity, comprising the steps of sequentially or simultaneously:
(i) forming an aqueous dispersion of a cationic surfactant, having a viscosity less than the final viscosity; and PA1 (ii) thickening the composition to the final viscosity with a nonionic or weakly anionic polymeric thickener. The thickener is selected from guar gum, polyvinylacetate, polyacrylamide, or a mixture of guar gum and xanthan gum containing no more than 10% by weight of xanthan gum. The polyacrylamides which are specifically referred to are the less anionic polyacrylamides. Quaternised guar gum was stated to be unsuitable. PA1 (i) copolymers of ethylene oxide and/or propylene oxide with small amounts of C.sub.8 -C.sub.24 side chains, for instance having the basic formula: ##STR1## (ii) Hydrophobically modified poly (ethylene oxide and/or propylene oxide/urethanes) for instance of the following formula: ##STR2## (iii) alkyl substituted poly (vinyl) alcohols, for instance of the following formula: ##STR3## Wherein: p=1 to 4 preferably 1 or 2 PA1 n+m=greater than 10 PA1 m=If p is greater than 1, m is such that the group involved constitutes less than 50 mole %, preferably less than 25 mole % of the polymer. PA1 R.sub.1 =a C.sub.8 -C.sub.24 linear or branched alkyl or alkenyl PA1 R.sub.2 =hydrogen or a C.sub.8 -C.sub.24 linear or branched alkyl or alkenyl PA1 R.sub.3 =a minimum of two R.sub.1 groups which can be substituted at any CH.sub.2 group along the polymer backbone. PA1 (i) amines of formula ##STR8## wherein R.sub.15, R.sub.16 and R.sub.17 are defined as below; (ii) amines of formula ##STR9## wherein R.sub.18, R.sub.19, R.sub.20 and R.sub.21, m and n are defined as below. PA1 (iii) imidazolines of formula ##STR10## wherein R.sub.11, R.sub.12 and R.sub.14 are defined as above. (iv) condensation products formed from the reaction of fatty acids with a polyamine selected from the group consisting of hydroxy alkylalkylenediamines and dialkylenetriamines and mixtures thereof. Suitable materials are disclosed in U.S. Pat. No. 4,661,269 corresponding to European Patent Application 199 382 (Procter and Gamble), incorporated herein by reference. PA1 (a) forming an aqueous dispersion of a softener having a viscosity of less than the final viscosity; and PA1 (b) thickening the composition to a final viscosity by including a polymeric material comprising molecules with a hydrophilic backbone and at least two hydrophobic groups per molecule attached to the hydrophilic backbone, except where the polymeric material is a hydrophobically modified nonionic cellulose ether.
The essence of the process of EP-51983 corresponding to U.S. Pat. No. 4,379,059 is to form a dispersion which is less viscous than is desired, and then thicken it with a polymeric thickener.
We have now found that a further class of polymeric materials is especially suitable as a thickener for fabric conditioning compositions. These materials provide dispersions the viscosity of which is relatively stable, and which do not bring with them any disadvantage which would make the product unsatisfactory for treating fabrics.